Solenoid valves are electromagnetically controlled industrial devices used in industrial control systems to adjust the direction, flow rate, speed, and other parameters of the medium. There are many types of solenoid valves, each playing a different role in the control system. The most common types are check valves, safety valves, directional control valves, and speed regulating valves. Solenoid valves are controlled by electromagnetic effects, primarily through relay control. This allows solenoid valves to be used with different circuits to achieve the desired control, ensuring both precision and flexibility. The rod-shaped component is the electrically controlled valve stem; electromagnetic force opens or closes the valve.
The following example uses a pneumatic system to illustrate the application of solenoid valves in industrial control. A pneumatic system is a control system that uses gas as the energy medium. In a pneumatic system, this energy medium is usually air. In actual use, the volume of air in the atmosphere is compressed to increase its pressure. Compressed air primarily performs work by acting on pistons or vanes.
In a pneumatic system, the solenoid valve's function is to adjust the various states of compressed air according to control requirements within the control system. A pneumatic system also requires the cooperation of other components, including power components, actuators, switches, display devices, and other auxiliary equipment. Power components include various compressors, and actuators include various cylinders. These are all indispensable parts of a pneumatic system. The valve body is a crucial device for implementing the control algorithm.
For example, a check valve allows compressed air to enter the air tank from the compressor, and prevents the compressed air from flowing in the opposite direction when the compressor is turned off; a safety valve can discharge compressed air when the pressure in the air tank exceeds the allowable limit; a directional control valve controls the direction of movement by alternately pressurizing and venting the two ports of the cylinder; and a speed regulating valve can easily achieve stepless speed regulation of the actuator.
Solenoid valves can be used not only in pneumatic systems, but also in hydraulic and water-pressure systems. For example, low-power, oil-free small solenoid directional valves do not require oil supply to the seals, and the discharged gas will not pollute the environment. They can be used in the food, pharmaceutical, and electronics industries.
Solenoid directional valve
Today, solenoid valve technology, combined with control technology, computer technology, and electronic technology, enables a variety of complex control applications. For example, solenoid valves can be used in intelligent control and wireless control technologies. Because solenoid valves can be controlled electromagnetically, they can interface well with various modern electronic systems, which is a major reason for their widespread use.
Solenoid valves have been widely used in various fields of production. With the improvement of electromagnetic control technology and manufacturing process, solenoid valves can achieve more precise control and play their role in different pneumatic and hydraulic systems.
Programmable Logic Controller (PLC) --- Stick
In recent years, with the development of large-scale integrated circuits, programmable logic controllers (PLCs) based on microprocessors have developed rapidly. PLCs are playing an increasingly important role in motor operation control, solenoid valve opening and closing, product counting, temperature and pressure setting and control, and other aspects.
A Programmable Logical Controller (PLC), often abbreviated as PC or PLC, is an industrial control device invented in the late 1960s. The Japan Electrical Control Society defined a PLC as follows: A PLC is a device that stores control programs, including logic operations, sequential control, timing and counting, and arithmetic operations, in the form of a string of instructions in its memory. Then, based on the stored control content, it controls production equipment and processes through analog and digital input/output components.
PLC is developed based on computer technology and automatic control theory. It is different from ordinary computers and general computer control systems. As a special type of computer control device, it has its own characteristics in terms of system structure, hardware composition, software structure, I/O channels, and user interface.
In principle, programmable logic controllers (PLCs) and computers are essentially the same. To adapt to industrial control, PLCs operate on a scanning principle, meaning they scan the entire program repeatedly until the system stops. This is because PLCs evolved from relay control, and the CPU's scanning time for the user program is much shorter than the relay's action time. By using a cyclic scanning method, this contradiction can be resolved. The cyclic scanning operation is a key difference between PLCs and ordinary computer control systems.
Although the components of various PLCs differ, their basic structure is similar, generally consisting of a CPU, memory, input/output devices (I/O), and other optional components. These optional components include a programmer, external memory, analog I/O panels, communication interfaces, and expansion interfaces. The CPU is the core of the PLC; it inputs various instructions and completes predetermined tasks, acting as the "brain." Advanced control algorithms such as self-tuning, predictive control, and fuzzy control have also been applied to CPUs. Memory includes random access memory (RAM) and read-only memory (ROM). Typically, the program and all fixed parameters are stored in ROM, while RAM provides space for storing real-time data and calculating intermediate variables during program execution. The input/output system (I/O) provides channels for inputting process status and parameters into the PLC and for outputting real-time control signals. These channels can include analog inputs, analog outputs, digital inputs, digital outputs, pulse inputs, etc., making PLCs widely applicable.
Early PLCs were primarily used for sequential control. Sequential control refers to the automatic, sequential operation of various actuators in a production process under the influence of control signals, following the order of the technological process. The application of PLCs greatly promoted the development of assembly line technology.
Today, PLCs are increasingly used in closed-loop control. Moreover, with the development of their expandability and communication capabilities, they are also being applied more and more in complex distributed control systems. Since its invention in 1969, the PLC, based on mature and effective relay control concepts and design ideas, has continuously utilized new technologies and devices, especially in conjunction with the rapidly developing computer technology, gradually forming a relatively independent emerging technology with a variety of distinctive product series. It has also gradually developed into an effective and convenient way to solve automation problems. The PLC's comprehensive functions, modular structure, ease of development, convenient operation, stable performance, high reliability, and high cost-effectiveness make its application prospects in industrial production increasingly promising. Furthermore, with the development of integrated circuits and the advent of the network era, PLCs will undoubtedly have even greater applications.
Currently, major PLC manufacturers are concentrated in developed countries such as Japan and the United States, and China's domestic PLC production and manufacturing technology still lags behind these countries. As an indispensable part of realizing industrial automation, vigorously developing PLCs is very important and has far-reaching significance for my country.
Industrial Computer --- 槊
Computers have dramatically changed our lives in recent decades. They have also found applications in industry, resulting in industrial computers. Simply put, industrial computers are computers used in industrial settings, and because of this industrial application, they differ from ordinary computers in several ways.
Industrial computers have different uses; they are mainly used for industrial control, testing, and other fields. A typical application of an industrial computer is to obtain external data through a standard serial port (RS232/485, etc.), perform calculations through the computer's internal microprocessor, and finally output the data through a display screen or the serial port. In this way, a calculation process is realized on an industrial computer. Obviously, this is completely different from the entertainment, office, and programming applications of ordinary computers.
Furthermore, industrial computers differ in their components. The diverse environments in which industrial computers operate inevitably lead to differences in their components compared to general-purpose computers. For example, industrial computers may lack a display screen, possess multiple serial ports, use dedicated industrial control CPUs, and have a very small system board area. All these characteristics reflect the differences in the composition of the two types of computers. Due to the harsh environments of industrial control, specialized components are often required to construct industrial control computers. For instance, some applications require a wide operating temperature range; many industrial computers can operate within a temperature range of -20°C to 80°C. Other applications require components with higher stability, such as those resistant to strong interference. These characteristics are closely related to the intended use of industrial computers. Precisely because of their diverse functions, different industrial computers also have different interfaces, resulting in lower versatility compared to ordinary computers.
The software systems of industrial computers differ from those of ordinary computers. Industrial computer software systems are relatively simple, primarily implementing a specific function. Furthermore, because industrial computers typically use slower processors, the requirements for program writing are higher. Industrial computers usually use simulation environments to develop programs and run them offline. Ordinary computers, on the other hand, have a large number of general-purpose applications, very fast processors, and their software development systems are entirely on the machine itself, requiring no external environment support.
Industrial computer interfaces
Everything has two sides. Industrial computers still share more similarities with general-purpose computers. For example, although they use different CPUs, these CPUs are from the same product line and have the same internal structure; the bus structures of the two types of computers are basically the same, and many industrial computers are simplified versions of general-purpose computers; and many industrial computers have the same or compatible interfaces as general-purpose computers.
Below, we will use a data acquisition system as an example to illustrate the actual process of developing an industrial computer. First, we investigate our development goals. Based on these goals, we select a typical industrial computer architecture, choosing the CPU, peripheral circuits, etc., used in industrial control. Then, we select a simulator and debugger, and develop the main control program on a PC. During program development, we need to design programs for signal acquisition, signal analysis, and storage. Finally, we burn the completed program into the ROM of the industrial computer, and then remove the peripheral simulator and debugging tools. A complete industrial computer is then ready for use.
Today, industrial computers have become an indispensable component in industrial applications. They possess the characteristics of computers and the practicality of industrial equipment, and will play an irreplaceable role in the future automation process.
Applications of microcontrollers---
A microcontroller is a computer that integrates a central processing unit, random access memory, program memory, timers, and various I/O interfaces onto a single silicon chip. Its main characteristics are small size, light weight, and good anti-interference and reliability, making it an indispensable component in industrial control.
Since its invention in 1976, microcontrollers have seen tremendous development. Currently popular microcontrollers include Intel's MCS51/96, Motorola's MC series, and Zilog's Z8 series, while many newer and more powerful microcontrollers continue to emerge.
The difference between a microcontroller and a conventional computer lies in the latter's integration. This sacrifices the microcontroller's versatility in a broad sense, making it primarily suitable for industrial control or integration into products. Consequently, the performance development of microcontrollers cannot be compared to that of conventional computers. However, for industrial applications, the speed of a microcontroller is sufficient, and it has its own unique advantages in industrial applications.
The core of a microcontroller is the Central Processing Unit (CPU), which mainly consists of two parts: the Arithmetic Logic Unit (ALU) and the Control Unit. The ALU primarily includes an accumulator, register set, and arithmetic logic unit, and is the core of its processing power. The Control Unit is the computer's command core, including the instruction set, timing unit, and micro-operation control unit; its function is to complete data exchange between the CPU and external systems. Unlike ordinary computers, microcontrollers adopt a Harvard architecture, while ordinary computers use a von Neumann architecture. Microcontrollers separate data and program memory, while general-purpose computers use the same memory space. Microcontroller memory is divided into RAM and ROM. ROM includes various types such as PROM, EPROM, and EEPROM. The program is usually permanently stored in ROM. This variety of storage types makes microcontrollers more suitable for different industrial applications. Importantly, microcontrollers also have strong memory expansion capabilities, capable of meeting diverse storage needs.
The built-in timers and I/O interfaces of a microcontroller are indispensable components. Timers are easy to use, offer flexible control methods, and their accuracy fully meets the needs of general industrial control. Microcontrollers have a rich variety of I/O systems with strong input/output capabilities. The characteristics of timers and I/O are also a major feature that distinguishes microcontrollers from ordinary computers.
Early microcontroller development primarily focused on assembly-level programming, making microcontroller applications quite complex. While the instruction set of a microcontroller is very similar to that of a regular computer system, it also has its own unique instructions. For example, the bit-addressing of the MCS series microcontrollers is a unique addressing mode, enhancing its ability to handle Boolean algebra. In addition, the instruction format of microcontrollers is also quite specialized. The main development work for microcontrollers concentrates on interface technology, which involves expanding the microcontroller's external functionality. Microcontroller interface technology mainly includes parallel interfaces, serial interfaces, digital-to-analog converters (DACs) and analog-to-digital converters (ADCs), as well as interface extension technologies. Through these extensions, the microcontroller gains interactive capabilities and effectively utilizes its internal processing power. Today, with the development of microcontrollers, numerous high-level language development tools have emerged. These systems, through simulation, enable rapid development on higher platforms, paving the way for the widespread application of microcontrollers.
The primary purpose of microcontrollers is application, and the following examples demonstrate their wide range of uses. Industrial measurement and control is one of the main functions of microcontrollers. Microcontrollers have abundant I/O lines, and a large proportion of these microcontrollers are used in the automotive industry, enabling more intelligent processing in specific automotive systems. In automotive systems, microcontrollers, combined with sensors and fixed algorithms, can adjust vehicle conditions without the driver's awareness. Furthermore, with the increasing performance of microcontrollers, they are also widely used in computer networks and communication technologies.
Microcontrollers are now ubiquitous, increasingly relevant to our lives and permeating every aspect of our daily routines. A key characteristic of microcontrollers is their small size, reflecting their integrated nature; their internal structure is a simplified version of a standard computer system. By adding peripheral circuits, they can become complete systems. For example, a commonly used electronic scale incorporates a microcontroller, along with sensors, a display, and additional circuitry, forming an application system. Therefore, microcontrollers offer excellent scalability. Another example is the K85 computer-controlled intermediate-frequency electrotherapy device, which acquires data from patients and selects from several treatment prescriptions based on existing algorithms. Within each prescription, the intermediate frequency, waveform, and output current intensity can be adjusted according to the patient's condition. This demonstrates that microcontrollers possess powerful processing capabilities similar to ordinary computers, allowing for the addition of complex algorithms and robust data processing power. Microcontrollers can also be applied to computerized sewing machines, replacing many mechanical parts and providing patterns that traditional sewing machines could not achieve. Therefore, the application of microcontrollers in industry has significantly improved the intelligence of industrial equipment, increased processing power and efficiency, without requiring large spaces or complex equipment.
Microcontrollers have already played a significant role in facilitating our production and daily lives, and they will undoubtedly play an even greater role in the future construction of socialist industrialization.
Relay control---turn
Relays are a common control device in our lives; simply put, they are switches that turn on or off when certain conditions are met. The switching characteristics of relays are widely used in many control systems, especially discrete control systems. From another perspective, since electronic circuits designed for a specific purpose ultimately need to interact with some mechanical equipment, relays also serve as an interface between electronic and mechanical devices.
The most common type of relay is the thermal relay. Commonly used thermal relays are suitable for AC 50Hz and 60Hz circuits with rated voltage up to 660V and rated current up to 80A, providing overload protection for AC motors. They feature a differential mechanism and temperature compensation, and can be plugged into specific AC contactors.
Time relays are also a commonly used type of relay. Their function is as a time delay element. They are typically used in control circuits with AC 50Hz, 60Hz, voltages up to 380V, and DC up to 220V to connect or disconnect the circuit at a predetermined time. They are widely used in electric drive systems, automatic program control systems, and automatic control systems in various production processes for time control.
Intermediate relays, commonly used in control systems, are typically employed for relay control, signal transmission, and isolation amplification. In addition, there are current relays for limiting current, voltage relays for controlling voltage, static voltage relays, phase sequence voltage relays, phase sequence voltage differential relays, frequency relays, power direction relays, differential relays, grounding relays, motor protection relays, and so on. It is thanks to these different types of relays that we can control various physical quantities and complete a comprehensive control system.
Besides traditional relays, relay technology is also applied in other areas. For example, intelligent motor protectors are developed based on the working principle of three-phase AC motors and the analysis of the main causes of motor damage. It is a uniquely designed, reliable, multi-functional protector that can promptly cut off the power supply when a fault occurs, facilitating motor inspection and maintenance. This product features phase loss protection, short circuit, and overload protection functions, and is suitable for the safety protection and power limiting control of various AC motors, switch cabinets, distribution boxes, and other electrical equipment. It is a preferred accessory for the design and installation of various electrical equipment. The installation dimensions, wiring methods, and current adjustment of this technology are the same as those of the same model of bimetallic thermal relay. It is an advanced electronic product that directly replaces the bimetallic thermal relay. However, its true principle is still relay technology.
Relay technology has evolved and combined with computer technology to create programmable logic controllers (PLCs). A PLC is an advanced device that directly applies microcomputer technology to automatic control. It boasts advantages such as high reliability, strong anti-interference capabilities, comprehensive functions, small size, flexibility and expandability, straightforward and simple software, convenient maintenance, and an attractive appearance. Previously, elevators controlled by relays had hundreds of contacts. A single faulty contact could cause a malfunction, making repairs extremely difficult. In contrast, a PLC controller contains hundreds of solid-state relays and dozens of timers/counters, with power-off memory functionality and opto-isolated inputs and outputs. The failure rate of this control system is only 10% of that of relay-controlled systems. For this reason, relevant national departments have explicitly stipulated that new elevators manufactured since 1997 must not use relay control and must instead use PLC microcomputer control.
It can be seen that relay technology is ubiquitous in daily life, and its close integration with computers has further enhanced its vitality, enabling relays to better serve our lives.
Hydraulic transmission control system --- Meteor
Hydraulic transmission control is a commonly used control method in industry, employing hydraulic pressure to transmit energy. Due to its flexibility and convenience, hydraulic control has gained widespread attention in industry. Hydraulic transmission is the study of using pressurized fluid as an energy medium to achieve various mechanical and automatic controls. It utilizes these components to form various control loops, which are then organically combined to create a transmission system that performs specific control functions, thus completing the transmission, conversion, and control of energy.
In principle, hydraulic transmission is based on Pascal's principle, which states that the pressure in a fluid is constant throughout. Therefore, in a balanced system, a smaller piston experiences less pressure, while a larger piston experiences more pressure, thus maintaining the fluid's stillness. By transmitting pressure through the fluid, different pressures can be achieved at different points, thus realizing a force transformation. The hydraulic jack we commonly see utilizes this principle to transmit force.
Basic principle of hydraulic transmission
The components required in hydraulic transmission mainly include power components, actuators, control components, and auxiliary components. Among these, hydraulic power components are the parts that generate power for the hydraulic system, primarily including various hydraulic pumps. Hydraulic pumps operate on the principle of volume change, so they are generally also called positive displacement hydraulic pumps. Gear pumps are the most common type of hydraulic pump; they move fluid through the rotation of two meshing gears. Other hydraulic pumps include vane pumps and piston pumps. When selecting a hydraulic pump, the main considerations include energy consumption, efficiency, and noise reduction.
Hydraulic actuators are devices used to convert the hydraulic energy supplied by a hydraulic pump into mechanical energy. They mainly include hydraulic cylinders and hydraulic motors. A hydraulic motor is a device that performs the opposite function of a hydraulic pump, converting hydraulic energy into mechanical energy to perform work.
Hydraulic control components are used to control the direction of fluid flow, pressure, and flow rate to meet specific operational requirements. The flexibility of hydraulic control components enables hydraulic control systems to perform various activities. Hydraulic control components can be categorized by application into pressure control valves, flow control valves, and directional control valves. They can also be categorized by operation method into manually operated valves, mechanically operated valves, and electrically operated valves.
In addition to the components mentioned above, a hydraulic control system also requires hydraulic auxiliary components. These components include pipes and fittings, oil tanks, filters, accumulators, and sealing devices. Using these components, we can construct a hydraulic circuit. A hydraulic circuit is a control circuit composed of various hydraulic devices. Depending on different control objectives, we can design different circuits, such as pressure control circuits, speed control circuits, and multi-cylinder operation control circuits.
Based on the structure and characteristics of hydraulic transmission, the design of a hydraulic system begins with system analysis, followed by the creation of a system schematic diagram, represented using hydraulic mechanical symbols. Next, hydraulic components are selected through calculations, and then the system design and debugging are completed. The creation of the schematic diagram is the most crucial step in this process, as it determines the quality of the designed system.
Hydraulic transmission has a wide range of applications. For example, in the hydraulic systems of stacking and loading machines, as a type of warehousing machinery, it is used in modern warehouses to mechanize the loading and unloading of goods such as textile packages, oil drums, and wooden barrels. It can also be applied in production practices such as the hydraulic systems of universal cylindrical grinding machines. These systems are characterized by high power, high production efficiency, and good stability.
Hydraulics, as a widely used technology, has a promising future. With the in-depth development of computers, hydraulic control systems can be combined with intelligent control technology, computer control technology, and other technologies, thus enabling them to play a role in more situations and to complete the expected control tasks more precisely and flexibly.
